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    Subject[PATCH 13/16] x86: Remove cpumask games in x86/kernel/cpu/intel_cacheinfo.c
    Impact: remove cpumask_t from stack.

    We should not try to save and restore cpus_allowed on current.

    We can't use work_on_cpu() here, since it's in the hotplug cpu path
    (if anyone else tries to get the hotplug lock from a workqueue we
    could deadlock against them).

    Fortunately, we can just use smp_call_function_single() since the
    function can run from an interrupt.

    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: Mike Travis <travis@sgi.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Oleg Nesterov <oleg@tv-sign.ru>
    ---
    arch/x86/kernel/cpu/intel_cacheinfo.c | 41 +++++++++++++++-----------------
    1 files changed, 19 insertions(+), 22 deletions(-)

    diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
    index 43ea612..fb7f946 100644
    --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
    +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
    @@ -534,31 +534,16 @@ static void __cpuinit free_cache_attributes(unsigned int cpu)
    per_cpu(cpuid4_info, cpu) = NULL;
    }

    -static int __cpuinit detect_cache_attributes(unsigned int cpu)
    +static void get_cpu_leaves(void *_retval)
    {
    - struct _cpuid4_info *this_leaf;
    - unsigned long j;
    - int retval;
    - cpumask_t oldmask;
    -
    - if (num_cache_leaves == 0)
    - return -ENOENT;
    -
    - per_cpu(cpuid4_info, cpu) = kzalloc(
    - sizeof(struct _cpuid4_info) * num_cache_leaves, GFP_KERNEL);
    - if (per_cpu(cpuid4_info, cpu) == NULL)
    - return -ENOMEM;
    -
    - oldmask = current->cpus_allowed;
    - retval = set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
    - if (retval)
    - goto out;
    + int j, *retval = _retval, cpu = smp_processor_id();

    /* Do cpuid and store the results */
    for (j = 0; j < num_cache_leaves; j++) {
    + struct _cpuid4_info *this_leaf;
    this_leaf = CPUID4_INFO_IDX(cpu, j);
    - retval = cpuid4_cache_lookup(j, this_leaf);
    - if (unlikely(retval < 0)) {
    + *retval = cpuid4_cache_lookup(j, this_leaf);
    + if (unlikely(*retval < 0)) {
    int i;

    for (i = 0; i < j; i++)
    @@ -567,9 +552,21 @@ static int __cpuinit detect_cache_attributes(unsigned int cpu)
    }
    cache_shared_cpu_map_setup(cpu, j);
    }
    - set_cpus_allowed_ptr(current, &oldmask);
    +}
    +
    +static int __cpuinit detect_cache_attributes(unsigned int cpu)
    +{
    + int retval;
    +
    + if (num_cache_leaves == 0)
    + return -ENOENT;
    +
    + per_cpu(cpuid4_info, cpu) = kzalloc(
    + sizeof(struct _cpuid4_info) * num_cache_leaves, GFP_KERNEL);
    + if (per_cpu(cpuid4_info, cpu) == NULL)
    + return -ENOMEM;

    -out:
    + smp_call_function_single(cpu, get_cpu_leaves, &retval, true);
    if (retval) {
    kfree(per_cpu(cpuid4_info, cpu));
    per_cpu(cpuid4_info, cpu) = NULL;
    --
    1.6.0
    --


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